text:
What is the difference between GPS, GNSS and RNAV?
I would like to know the fundamental difference between GPS, GNSS and RNAV. How are they related each other? Are all/some of them synonyms?

As stated in the othe answers,

GPS is the US Global Positioning System
GNSS is an umbrella term that encompasses GPS as well as other nations' satellite systems that achieve essentially the same capability

RNAV is the aircraft capability that allows you to navigate from point to point, defined by Latitude/Longitude and independent of any ground-based system.  There are various ways that the hardware in the aircraft maintains its position.  It may use GPS sensors, it may use GLONASS, it may uses a combination of satellite systems, it may use DME/DME updates from ground-based navaids.  But the point of RNAV is that for the most part the procedures are agnostic with regard to how the position info is obtained.
Thus, you can have RNAV routes and approaches, meaning that the airway or approach segments are defined by Lat/Lon waypoints, and as long as your system meets defined accuracy tolerances (usually 1.0 NM enroute and 0.3 NM for an approach in the US), you can fly that airway or approach.  There are more stringent tolerances incorporated into RNAV(RNP) approaches, and these require that the system can monitor its accuracy and alert the pilot if the system isn't confident that its position is accurate to within a specified performance.  This can be set to match whatever is required on the approach; 0.1 NM is common, although there are other values that can be specified.
In the US, the FAA typically distinguishes basic RNAV approaches by designating them RNAV(GPS) in the title, as opposed to RNAV(RNP).  (The RNAV(RNP) approaches require a couple of additional things beyond basic RNAV, but those are beyond the scope of this question.)  Internationally, "RNAV(GNSS)" is often used instead of "RNAV(GPS)" in the approach title, but functionally they're pretty well the same thing -- it's simply a nod internationally to the fact that if your FMC knows where it is, the approach designer doesn't care which satellite system it's getting its position data from.
In the "old days", it was possible to have RNAV operations that worked by taking radial/DME data from a single VOR and creating a pseudo-VOR essentially whereever you wanted, and the HSI or other display would act as if the VOR were in the new location.  This was very early RNAV capability, in that it allowed you to fly a straight line course by keeping the HSI centered rather than flying VOR to VOR.  These days, that capability is pretty much gone, in favor of the much greater capability of GPS.

The last paragraph sounds like the pseudo-VOR mode of HSI is related to determining position from VORs, but those are two independent things. The HSI still behaves that way if displayed, just map display is used more often now instead. And most new systems probably still can fall back to determining position from VOR/DME distance and radial, just they prefer GPS when available.

@JanHudec  The old equipment with the pseudo-VOR was not what we'd consider today as RNAV in that it did NOT use Lat/Lon -- it simply "displaced" the VOR (which you had to be receiving) a specified distance on a given radial, and your HSI still worked like a normal HSI for a VOR (course select, etc).  The capability now to determine Lat/Lon using DME updates from several VORs is entirely different - real RNAV now, and an RNAV course now does NOT look like a traditional HSI -- no course selecting is available, the course is driven by the system. Two entirely different capabilities.

The CJ3 aircraft that I fly with (fairly) modern Collins ProLine 21 FMS still include the option for disabling the GPS input and using RNAV based solely on DME and VOR input. I have not used this in the real world, but it is one of the approved methods of flying VOR approaches, which I have done in training. I think that it would still work acceptably at high altitude (at/above FL180) through most of the areas within the US that I fly.

Is there an official reference for  “it's simply a nod internationally to the fact that if your FMC knows where it is, the approach designer doesn't care which satellite system it's getting its position data from.” Ty

Are you asking about the acronyms on their own or in relation to instrument approaches?
Generally speaking, GPS stands for Global Positioning System and is a satellite based navigation system built and maintained by the US government.
GNSS stands for Global Navigation Satellite System, which encompasses GPS as well as the Russian built and operated GLONASS (Global'naya Navigatsionnaya Sputnikovaya Sistema/"Global Navigation Satellite System" in Russian) and Galileo (EU) or Beidou (China).
RNAV stands for Area Navigation and is one of the main components of the US National Airspace System.
All of these things are forms of navigation used by aircraft and sometimes boats too.

RNAV no longer indicates ground based stations like VORs and DMEs.  It can certainly use that though the procedure (SID or STAR) may limit that.  DME\DME RNP 0.3 NA. It is primarily based on satellite GNSS systems.  In the past, it was used with pseudo VORs and IRS/INS systems.  Many FMS systems today can fall back to using the older technology when GNSS accuracy is reduced.

@wbeard52 I took that part of his answer to mean that the radio nav-aids were used as waypoints in the GNSS.

No, the statement "RNAV is generally based on the ground-based radio navigation beacons like VOR's" is simply wrong.  The RNAV systems certainly CAN navigate to a waypoint that corresponds to a VOR or to a fix that is also defined off of a VOR, but RNAV routes & procedures are increasingly based off of points defined by Lat/Lon that have no correspondence to anything ground-based. Also, do boats use RNAV?  Hadn't heard of that one before.

Not only is that wrong, but it is exact opposite of what it should be. Airways and procedures were in the past generally based on the ground-based radio navigation beacons and RNAV is the ability to use those that are not.

Global Positioning System (GPS) is a U.S. initiated, monitored and maintained system.
As Dave pointed out, GLONASS is maintained by Russia, Galileo by Europe and BeiDou by China.
All of these systems and others comprise the Global Navigation Satellite System (GNSS).  There is a subset of GNSS called satellite based augmentation system (SBAS).  Under this subset is the U.S. wide area augmentation system (WAAS), EGNOS by Europe, MSAS by Japan and GAGAN by India.
"Random" Area Navigation (RNAV) allows an aircraft to choose any course within a network of ground based stations or GNSS.  It is typically developed and flight checked (in the U.S.) and published as procedures.  In the U.S. you will see approaches titled RNAV (GPS)... that use procedures developed by the FAA.


text:
What is the step-by-step process to become a ground instructor in the US?
I would like to know about the whole step-by-step process to become a ground instructor in the US.
My understanding is that any previous pilot or CFI certificates are not needed. So, are only needed the FAA written tests (FOI/BGI/AGI/IGI)? And that's it? What about endorsements?
After passing the FAA written test, do I need to submit an application in the IACRA system to request the card, or it is done automatically?

You may want to check out this document from the FAA also linked in that document is this document which may shed more light on the matter

The general qualifications for an Instructor Rating require you have a
  combination of experience, knowledge and skill. Title 14 of the Code
  of Federal Regulations (14 CFR) part 61 requires that pilots must be
  able to read, write, speak, and understand the English language. If
  you cannot meet these requirements of English fluency, an airman
  certificate cannot be issued. For medical reasons, an appropriate
  limitation may be placed on the certificate.
You must pass the Fundamentals of Instructing Knowledge Test and a Flight or Ground
  Instructor Knowledge Test specific to the instructor rating sought.
  You may take these tests on the same day, and you do not have to take
  them in any particular order. An instructor rating obtained by passing
  the Military Competence Instructor (MCI) exam does not require the
  candidate to take the Fundamentals of Instructing (FOI) exam.
When
  applying for any additional instructor rating, you are not required to
  take the Fundamentals of Instructing Knowledge Test again. Once you
  have acquired a Flight Instructor Certificate, you are eligible to
  give ground instruction required for a Pilot or Instructor Certificate
  or rating, based on the ratings on your Flight Instructor Certificate.
  Because of this, it is not necessary to obtain a separate Ground
  Instructor Certificate since you would already have these privileges.

AskACFI breaks it down nicely here.

Yes, you need to complete your FAA Written Tests - FOI (if you're not already a CFI) + the particular GI test (Basic/Advance/Instrument).
You do NOT need any endorsement or sign-off to take the written test. Just study, schedule and attempt the test. +70% is all you need. The testing center proctor will only need the basics from you (ID/Address Proof).
After passing the written test, you need to start an IACRA application (Instructor > Ground Instructor > Standard). Then, you have two options:

Go to your local FSDO office (they'll most likely need an appointment). Once you're there, the person on-duty (Aviation Safety Inspector or otherwise) will be able to process the Ground Instructor certificate for you. You'll receive a temporary certificate to be able to exercise privileges, and the card will be mailed to you just like any other FAA Certificate. FSDO will do it for free. However, the drive and the long-waiting times can be the "cost" to do this.

OR

Get in touch with any DPE that you know, and they'll do the same thing as the FSDO. However, they might charge you. I did a couple of checkrides with a DPE and he was happy to process the my IGI/AGI for free since he was doing a checkride for someone else and I just met with him for a few minutes after he was done with the checkride. I've seen some DPEs charge $200 to do this (ridiculous!).

Thank you for this answer. There is an enormous variety of articles on the internet describing the AGI/BGI requirements and why you should do it, and none go into the practicalities of doing it.

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text:
Do I get two different certificate cards if I earn both a pilot and a ground instructor certificate in the US?
I would like to know if one will be receiving two separate licenses in case he/she earns a pilot certificate as well as a ground instructor certificate in the US.
Do the certificates come separately on two different plastic cards? If yes, does the certificate number change between them, or do they have the same number?

Commercial pilot certificate, CFI, and AGI; three different cards.  Same number on pilot and AGI, and the same number plus 'CFI' on the CFI certificate ie.  1234567 vs. 1234567CFI.

Which country are you asking about?

I just improved the question. It is for US.

Yes.. The certificate number will not change.  The flight instructor certificate includes CFI at the end of your number.

§61.5   Certificates and ratings issued under this part.
  (a) The following certificates are issued under this part to an applicant who satisfactorily accomplishes the training and certification requirements for the certificate sought:
(1) Pilot certificates
(2) Flight instructor certificates.
(3) Ground instructor certificates.

Part 63 provides guidances on flight engineer and flight navigator certificates.
Part 65 provides guidance for ATC tower personnel, mechanics, repairman, parachute riggers, and dispatcher certificates.

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text:
How are "charter" and "passenger" flights defined in the AIDX standard?
I'd like to know the difference between these flight types in the IATA AIDX standard; specifically, for use in fuel order notifications.

Does that relate to the "Standard Weight" for a pax, or the Airport Zone (GA, charter...). Do you have a specific document to look into?

The hyperlink points to a generic company homepage not to any relevant information. And what are "these flight types"?

I know this question is 3 years out of date, but I thought I'd answer anyway. My answer is only applicable to Aviation Info Data Exchange (AIDX) schema 16.1.
As far as I know, there is actually no item in the format specifying the type of flight. But most systems I've come across have some coupled business logic that will make an AIDX request with the form of SheduleRQ and push this to a database.
If the flight isn't in the database it will make a further PublicStatus request to determine if the aircraft info should be shown to the public.
This might be a work around at the moment, but soon enough (2023-2025) AIDX will be integrated into AIDM and with all luck, unacknowledged requests will be a thing of the past.

authors: Роман Самойлов


text:
Do cabin evacuation tests include passengers with limited mobility?
When doing the evacuation drills to ensure people can leave the plane in 90 seconds, are they tested with disabled people, ones in wheelchairs or, like myself, people who have difficulties walking and use crutches? I would never be able to jump on the slide or even evacuate in 90 seconds so what would that mean for me? Would I just be left behind?

Related question about realism of evacuation tests.

Same for young children, elderly, people with broken legs, etc. That said, 90 seconds is a limit for the test. Nobody said 90 seconds is the limit to survive a crash.

You don't necessarily have to "jump" on the slide. In an emergency any way you get out is fair game, if you would have a problem "jumping" as shown in movies, you could just kind of fall into it, although your risk of injury would be higher. There is probably somebody at the bottom of the slide to help you off and away to safety. That being said though, if I had a disability I would opt for seats closer to exits if possible.

@RonBeyer in the same way I opened a saving account in case I win the lottery I guess ?

About 6% of the participants in those tests sustain injuries, mostly abrasions and bruises, but more serious injuries up to and including permanent damage have been recorded. Because of child labor laws and safety concerns, the age mix for the tests has been changed to exclude minors, and allow the aircraft manufacturers to exclude participants over 60 who are the most likely to be injured. (In the latter case, they are required to increase the number of middle-aged participants significantly.) So, unfortunately, it is just not ethically possible to make the tests more realistic.

As @mins said in the comments, the 90 seconds is a limit for a evacuation test. Having equal test requirements means that all planes have a minimum, similar evacuation capability.
That said, the conditions of an evacuation test are rather benign: people participating in them know nothing is really wrong, there are no hazards like smoke or fire, and the plane is in a normal attitude (no broken gear or hull, engines stopped). See

.
In real emergencies, the time to evacuate may be greater than 90 seconds, and the crew and ultimately the captain has the responsibility to ensure that everyone has been evacuated safely and leave the ship the last. So, crew incapacitation left apart, you wouldn't be left behind.

That is a very good question, and from my experience with flight test, I would say that I would guess no. All of our crews had FAA Class 3 medicals. I would have to research the certification requirements.
With that said, there is increasingly a spotlight put on the airlines when passengers with disabilities are mistreated.


text:
Where can I find documentation that state sales tax was paid in the 1980s when an aircraft was purchased?
I am going from a sole owner to a partnership with two others in a Cherokee 140.  The state wants proof that state sales tax was paid in the 1980s when a family member originally purchased the airplane.
I have informally been a partner in the airplane since that time and have been paying half the bills. My partner recently passed away. I'm sure the state sales tax was paid but cannot find any documentation. They won't process the new registration until I can provide documentation that the state sales tax was paid, or I have to pay the fee again.
Where can I find a record that the state sales tax was paid when the aircraft was originally purchased by my family member?

Welcome to the site! I assume you're in the USA? It might be helpful to mention which state you're in. You can request all the documentation that the FAA has for an aircraft, but the FAA has nothing to do with state sales tax. It's not really an aviation question as such, it's more about how to find old tax records in your state. If you don't get a good answer here, you might try money.SE

This is really not an aviation-related question - it's a tax and recordkeeping question. It  might be more topical over on [money.SE], but really the answer is probably going to be "You need to find records demonstrating the tax was paid, like a cancelled check or a receipt for payment." (Alternatively consult a local CPA to see about telling the tax authority in your state "You're talking about a 30-year-old sale, you're clearly out of your minds - get stuffed." - I believe the IRS is limited to 10 years, but your state's law may say otherwise…)

You may have already done this, but the Wisconsin Department of Transportation's website says, "If you have questions regarding sales or use tax contact the Department of Revenue at (608) 261-7694."

This is a state level issue (here in the US) and you will have to contact the state in question. While aircraft are registered federally the sales tax is state imposed (and collected). If the family does not have the documentation you may have to go through some hoops to get it. Its also important to add what state you are in as that may change the answer to the question.
Furthermore depending on how you are setting up the new partnership there are tax implications to that as well. You should talk to a lawyer about the various ways this can impact things. Unfortunately in the eyes of the state you had no stake in the plane (despite your informal ownership, the state is only worried about formal ownership).

The aircraft is in Wisconsin.


text:
Can a C152 land VFR in Miami International Airport (KMIA)?
I know that it is a Class B airspace and VFR aircraft should request clearance at least 1 hour in advance before entering. The question is more related to MIA operations restrictions due to airliners.
It is possible to land with a C152 there, apart from being above VMC weather minimums (3 SM visibility and clear of clouds) and having 2-ways radio and transponder Mode C? How much is the landing fee? How can I gather all the information for GA and light ACFT operations in MIA?

I don't see why not... They might even make the airliner slow down for you.

Sure can if your C-152 is equipped with at least a two way VHF radio and a transponder with altitude reporting capability.  And you hold at least a PPL with current medical or are a student pilot with current medical and have a logbook endorsement from a CFI to fly there.
According to the A/FD entry for KMIA, all GA arrivals should file request a clearance at least three hours in advance of their arrival (this three hour notification is only for international GA flights requiring customs).
As with flying into any Class B airport, you will have to be on top of your game and able to quickly and accurately comply with ATC instructions.  Have all you charts and plates ready to go, especially taxi diagrams and frequencies.  Expect taxiing delays and instructions.  Wake Turbulence avoidance procedures should be used and anticipated.


text:
Does a pilot have to request altitude changes when receiving flight following?
Let's say that during a VFR flight the pilot requests flight following from ATC, giving information about the aircraft type, type of equipment, destination and cruise altitude. ATC responds by giving a squawk and saying "maintain VFR".
In that scenario:

Does the pilot have to request an altitude change from ATC during flight following, even though the flight is under VFR?
Or, does he need to just advise ATC and start descending/climbing to another VFR altitude?
Or, is it not necessary to say anything to ATC about VFR altitude changes during flight following?

Finally, where can I find information about the regulations for flight following? I could not find anything in the FAR/AIM.

Depends on whether you are in controlled airspace

To add to the answers, requesting an altitude change is not necessary; advising an altitude change is also not necessary, but usually appreciated (at least by me).

No, you wouldn't need to advise of changes if all that they instruct is "maintain VFR."

91.123(b): "... no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised."

It would depend on the instruction received.  Let's say, after departing from class 'C' airspace, they told the pilot, "maintain VFR and resume own navigation," they are giving him freedom to choose his own headings and altitudes.
On the other hand, if the controller said, "maintain 5,500 and turn heading 030," then the pilot would need to cancel flight following or make a request to change instructions.
Bottom line: don't not do something they do tell you to do.

A VFR pilot typically advises ATC of altitude changes when outside B, C, and D airspace.  Unless within B, C, or D, ATC only issues advisories and cannot "clear" or otherwises direct VFR traffic.  One can argue they assume responsibility for your seperation the moment a direction is given.  Very few controllers will accept that liability.
When in class B, C, and D a controller may assign heading and altitude changes or restrictions, but outside of these evironments a VFR pilot is pretty much left to his own devices within the confines of the regs.
Good article here.

They'll give directions in class E airspace above/below/around class B/C/D airspace any time that it makes managing IFR traffic in/out of those areas easier.  In particular, they'll often restrict altitude (often block, e.g. at or below X, rather than exact) but leave lateral nav to you.  They'll also usually "suggest" beginning descent to your destination, and the handoff to tower or CTAF usually comes shortly after.

Article link no longer works

Outside of Class B airspace ATC has no responsibility for ensuring your separation from other VFR targets, and outside of Class C airspace has no responsibility for ensuring your separation from IFR targets. All that are required are traffic advisories and safety alerts. Of course allowing you to run straight into another plane is quite frowned upon.


text:
How do I become a flight test engineer?
I would like to know the whole process to become a flight test engineer (FTE).
Do I need to take any FAA specific flight test engineer certificate, apart from an aerospace engineering degree? Do I also need a minimum of flight hours with a commercial pilot certificate?

"Flight Test Engineer" sounds like a job description, since there is no FAA requirements that I can find that specify any official requirements for that. If that is the case, this is going to be highly dependent on the organization that you end up working for... The FAA has a "Flight Engineer" rating, but that is entirely different and very few people have/get that rating.

What is the difference between the "Flight Engineer" and "Flight Test Engineer" FAA certificates? I would think it is worth to get a Flight Engineer certificate to become a FTE.

This very long audio podcast contains an interview with a flight test engineer and mentions the difference to "regular" flight engineers.  Highly recommended listening for anyone considering a career in test flying!

@FrancescoC A "flight engineer" is the third guy in the cockpit running the engines. It really doesn't have any tangent to a "flight test engineer", and because there aren't any modern aircraft that require a flight engineer it isn't a rating worth getting, and won't help with becoming/being an FTE.

I suspect, @RonBeyer, that an FE rating would be useful if one were interested in flying historic aircraft that need an FE. That, however, is quite different than being a Flight Test Engineer.

@FreeMan That may be true, if you look at the FAA Statistics for 2015 Table 16, the FAA only issued 29 FE ratings last year. I'm not sure if thats mostly for historic aircraft, or just at the request of some companies still flying old equipment that needed an FE. If you look at Table 1, you can see the FE's are declining very quickly.

Go to college and get an engineering degree, preferably in Aerospace Engineering or Mechanical Engineering with an Aerospace emphasis.  You may also want to pursue a Masters in this area after your Bachelors.
Seek out the best schools you can get into; the biggies in aero are Georgia Tech, University of Michigan, Purdue, University of Washington, and MIT.  But there are a lot of other schools out there with fine aero programs as well and attending there doesn't limit your job opportunities.
Study hard and get good grades.  If you can't hack your freshman and sophomore years, engineering may be a bad choice as a field for you; seek a different major.  On top of that, I strongly suggest you get involved with extra curricular engineering projects or clubs in your department.  This will give you a lot of hands on engineering experience and help build up a knowledge base for you of how to be a good engineer.
I'd also get involved with either a RC airplane club, or better yet, join a chapter of the Experimental Aircraft Association and participate in the flight testing of home-built aircraft.  Again, it starts giving you a lot of hands-on experience in the flight testing of airplanes, which looks really good on a resume.  You can also get a couple of good references this way.
In your junior or senior undergraduate years, start looking for co-op or internship opportunities at the major OEMs, i.e., Boeing, Northrop-Grumman, Cessna, Beechcraft, Airbus, Piper, HondaJet, Gulfstream, etc.  Preferably seek out internships in flight testing.
Finished with school?  Time to land your first job in flight test.  Attend your school's career fair and chat with the reps from the OEMs.  File applications for jobs on OEM careers sections.  Get your LinkedIn page set up.  It's now time to get references from your internship supervisors.  This first job is always a challenge as many OEMs are looking for experienced people and there are very few entry level roles.  You first job may not be in flight testing and will probably not be very glamorous.
Aerospace is a limited and challenging field to get into.  Work is also limited to certain areas of the nation, primarily Seattle, LA Area/SoCal high desert, Dallas, Wichita, Greensboro, or Savannah.  In addition, the business is quite fugitive, having many boom and bust cycles.  Layoffs happen very frequently and you may have to move from place to place to find work.  Starting salaries and benefits packages can be spartan.
Flight testing may or may not be as glamorous as you think it is.  Your primary duties will be generally doing test plans and reports for flight test operations, rigging aircraft of a/c systems with sensors, wiring and data collection boxes, possibly some 3-D CAD modelling.  Even the engineers on the aircraft are sitting at crew stations monitoring data collection.  After that you'll be doing data analyst activities, crunching numbers, etc.
A PPL or CPL is not necessary to be a flight test engineer.  Test pilot is another story altogether and is considerably more difficult.  There are civilian routes into this business but are extremely difficult to obtain.  Most test pilots get their education by becoming military pilots and attending either the USAFTPS at Edwards AFB or the USNTPS at NAS Pax River.  In addition, most of the test pilots at the major OEMs come from the military route and, IMO favor the military guys over non-military, particularly in flight testing high performance military aircraft.  Near as I know there are no requirements from the FAA to become a test pilot but the only private test pilot school in the nation is the National Test Pilot School in Muroc, CA.  They require applicants to possess an engineering degree, a CPL and at least 750 hours total time in fixed/rotor wing.  With an 11 month course to obtain a Masters of Science in Test Piloting costing an astounding $960,000.00, you will definitely need corporate sponsorship.  There are a few firms which will do this.  Burt Rutan's Scaled Composites in Muroc promotes test pilots from its engineering corps.  So does Cirrus in Duluth, MN.  But the competition to obtain these slots is fierce.  All in all, if you want to be a test pilot, go the military route, either in the Military Academies or a ROTC unit at your college.

For #1 dont forget Electrical Engineering and Computer Scienctists. If a plane is getting upgrades then its 90% chance it's an avionics integration which is all EE/CS stuff.

There are no FAA requirements for becoming a flight test engineer (FTE); however, EASA has a formal certification process.  This also means that you can become an FTE with no flying training at all.
There are several well-traveled roads to becoming a Flight Test professional.  I illustrate nine broad paths here.  For specifics on becoming an FTE in the military, including attendance at a Test Pilot School (which is not required), I wrote this.
Many start their flight test career at the widest part of the funnel.  That is to say that, normally an organization will hire engineers and provide them with the training and development they need to become FTEs.  This is good way to enter the pipeline.
There is a global organization of FTEs known as the Society of Flight Test Engineers (www.sfte.org), and it includes people who have become an FTE in every possible way.  Its members can answer general questions, like the one posed above, and more specific questions that may apply at particular milestones along one's personal journey.  SFTE has also formally responded to EASA's requirement for formal certification here.


text:
During VMC conditions in terminal airspace (class B), does the pilots have to strictly follow separation standards issued by ATC?
Is it common for pilots to breach separation standards in terminal airspace while the conditions are VMC? I'm interested primarily in commercial aircraft that have scheduled operations in major airports.
I know there are Loss of Separation events reported to FAA - is that a small subset of actual incidents? Are these reports predominantly for during IMC conditions?

What do you mean? There are no separation minima for pilots to follow, only for controllers. Depending on airspace class, either ATC needs to provide separation - and does so - or not. Pilots are never responsible for ensuring ATC separation

The question in the title doesn’t really match the question body, can you say more precisely what you’re looking for? And can you clarify what you mean by “terminal airspace”? The ATC separation services are different in different airspace classes. For example, ATC (in the US)  separates all traffic in class B, but not in C/D.

I guess by terminal airspace I was referring to class B  airspace. So, I calculated distance between aircraft pairs 50 nautical miles around DFW from flight track data. The distances calculated fall under the prescribed separation standards. And it happens more during VMC conditions (based on ceiling and visibility values). I guess my question is whether this loss of separation is expected?

@distributedconscious - I am in the DFW area. During VMC, ATC will confirm that aircraft are in visual contact with each other. They will then inform pilots to maintain visual separation. No exact distances are prescribed. When a pilot acknowledges they have visual contact, it is then up to the pilot to “see and avoid”. If the pilot is within the 30 mile mode C veil, but outside (under) the Class B airspace, the pilot can fly VFR without ATC services. In non-participating VFR flight, the pilot is solely responsible for separation. ATC will separate non-participating from participating.

@distributedconscious - Participation in ATC separation services is strictly voluntary outside (under and around) the DFW Class B. If you are going to enter the Addison (KADS) airspace, you have to participate in DFW separation services provided by TRACON 10 until handed off to the Addison Tower. Otherwise, if you are a pilot in command of a non-participating flight, you are responsible to see and avoid other traffic. A lot of the flights you are seeing on Flight Radar and other services may be GA aircraft flying in VFR. That may be why you see a difference during IMC.

@DeanF. Thank you! that's very helpful!

There are several different separation standards which ATC attempts to maintain between aircraft. Note that only one of the standards below needs to be maintained; if one is valid that is sufficient. I'm answering for USA-land as you mention the FAA in your question.
Vertical Separation
Aircraft may be separated vertically. If one aircraft is directly above a point on the earth and is at an altitude of 4000 feet, and another aircraft is directly above the same point at an altitude of 6000 feet, they are separated.
IFR aircraft must be separated from other IFR aircraft by at least 1000 feet. At or above FL290 this increases to 2000 feet if either aircraft is not Reduced Vertical Separation Minima-capable (RVSM), and above FL410 the minimum is 2000 feet no matter what (and sometimes more for certain military or supersonic flights).
Within Class B, Class C and TRSA airspace, IFR aircraft are separated from VFR aircraft by at least 500 feet. This also applies to known VFR aircraft operating in the associated Class C outer area.
Within Class B and TRSA airspace, VFR aircraft are also separated from other VFR aircraft by at least 500 feet. VFR aircraft must receive an explicit clearance into Class B airspace, allowing them to be separated from other VFR aircraft. In the case of a TRSA this only applies to aircraft requesting radar services.
Lateral Radar Separation
Vertical separation is not terribly interesting. Let's instead look at lateral separation, where the two aircraft are at the same altitude, so it would not be good if they were also above the same point on the earth.
The absolute bare-bones basic standard of separation is: Did the planes hit each other? This is a highly undesirable situation. For VFR aircraft operating in Class E/G airspace, this is the only minimum that matters, and pilots will apply it themselves using the "see and avoid" principle: They see other aircraft and maneuver to avoid hitting them. This is also the only separation standard that ATC maintains between two VFR aircraft in Class C/D/E airspace, and in fact separation isn't truly lost until the planes trade paint. (Then it's a bad day for everyone.)
At a slightly higher level there is target resolution. This can be applied between VFR-VFR or VFR-IFR aircraft operating in any type of airspace, except in Class Bravo when one aircraft weighs more than 19,000 lb or is a turbojet. Target resolution means the controller issues instructions, traffic advisories, and safety alerts to ensure that the radar targets on their screen are "resolved," which is to say they do not ever touch each other. There can be some error in the positioning of the targets on the screen but if two aircraft are very near each other the difference between the two errors is likely to be minimal—so if the displayed targets never touch, you can be sure the aircraft themselves certainly don't.
Getting into defined radar separation:

In Class Bravo airspace, VFR aircraft are separated from IFR/VFR aircraft weighing more than 19,000 lb by 1.5 nautical miles.
In the terminal environment (i.e. TRACONs, and enroute facilities at FL230 and below where certain requirements are met) IFR aircraft are separated by 3 NM. This can be reduced to 2.5 NM on final approach, subject to various extra rules and procedures.
If the aircraft is more than the prescribed distance from the radar antenna, or if the system indicates a need, or above FL230, IFR aircraft are separated by 5 NM.
At or above FL600 separation increases to 10 NM between IFR aircraft.

Passing or Diverging Separation
Terminal facilities are authorized to discontinue the use of radar separation and fall back on target resolution if aircraft are on tracks which will never meet (either because one target has passed the projected track of another, or if they are opposite-direction because the two targets have passed each other). Enroute facilities can do this as well but have more onerous rules.
Wake Turbulence Separation
Smaller aircraft operating behind heavier aircraft (defined based on maximum takeoff weight) are afforded increased separation, ranging from 4 to 10 NM instead of 3 or less.
Non-Radar Separation
Almost invariably, using non-radar separation will provide a greater actual distance between aircraft than using radar separation, so it is not usually applied in areas of radar coverage. For myself I don't know much about it, having never applied it.
Lateral
Aircraft may be separated by assigning them to fly on different airways, or different radials or arcs of navigational beacons, or other such procedures.
Longitudinal
Aircraft operating along the same airway, or at the same airport, may be separated based on time and speed.
Visual Separation
Airborne separation may be reduced below the applicable minimum if visual separation is used. Some other form of approved separation must exist before and after the application of visual separation, and visual separation is not allowed above FL180 (i.e. in Class A airspace) or if the leading aircraft is a super weight class.
Pilot-applied visual separation may be used if the pilot of one aircraft reports another aircraft in sight and confirms that they will maneuver to maintain their own separation (i.e. they don't hit). Tower-applied visual separation may be used if the tower controller can see both aircraft and issues instructions to ensure they don't hit.
Visual separation is not prohibited if the weather is below VFR minima (IMC) but will likely have limited usefulness because some other form of approved separation must exist once the pilot or controller loses sight of the aircraft. Some facilities have it written in their local procedures that tower-applied visual separation is assumed to be in effect whenever the weather is better than certain minima.
Runway Separation
Not as relevant to your question but provided for completeness. Runway separation is flight-rules agnostic; the controller will apply it regardless if a flight is VFR, SVFR, or IFR. Based on the category of aircraft (category being defined in relation to engine type and number, and for single-engine propeller planes also weight) and type of operation (arrival-arrival, arrival-departure, departure-arrival, departure-departure) ATC will ensure 3000, 4500, 6000 or "the entire runway's worth" feet between aircraft operating on the same runway. They will also ensure an aircraft or vehicle does not cross a runway another aircraft is operating on.

So to finally answer your question: Pilots do not apply "separation standards" in any type of airspace, except that they are required to avoid hitting other aircraft if they see them in time. Instead, ATC applies separation minima which change based on the type of flight rules, type of aircraft, and airspace in which the aircraft is operating. In order to make sure these separation minima are maintained, pilots are required to comply with ATC clearances and instructions, or else have a really good reason why not.

Why does the required IFR-IFR separation double above FL600?

@Vikki, probably for the same reason separation increases from 3 to 5 NM at FL230. I'm not certain what that is, but it's probably because aircraft operating at higher altitudes will tend to have faster groundspeeds so you want more wiggle room in case separation is lost. Also higher aircraft will by necessity be farther from the antenna (which measures slant-line distance) so will have more uncertainty associated with their position... though 60,000 feet is only 10NM, so not a huge difference compared to the 290-mile range of an air-route surveillance radar.

The only “separation standard[] issued by ATC” is visual separation, and as long as you don’t literally hit the other plane, you have complied with it. The penalty for non-compliance is usually death, so we pilots take that pretty seriously.
All other types of separation are provided by ATC via some sort of clearance or instruction that the pilot must comply with.  If not, the pilot can be violated (which might mean a fine or license suspension) for failure to obey said clearance or instruction, not for any resulting loss of separation per se.
In practice, a loss of separation usually happens because some non-participating aircraft suddenly wanders into the path of a participating one. That shouldn’t happen in class A/B/C/D since non-participating aircraft shouldn’t be there in the first place, but it does happen now and then when someone gets lost; it’s fairly common in class E/G, where participation is optional.


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Do turbofan nacelles generate lift?
Since they are essentially an annular wing, how much do they contribute if at all to an aircraft's total lift? Would the effect of this lift be noticeable enough to help cancel out the drag they produce?

Most jet nacelles contribute little or no lift, but there is at least one highly notable exception.
The airflow inside the nacelle is dominated by the engine and any chance to create differential pressure between upper and lower leading sections is kept negligible in order not to disrupt the intake flow.
The outside is more of a stubby fuselage than an annular wing and low drag dominates the design. The avoidance of interference with the leading edge of the wing, part way along and just above, is also a major consideration for the upper profile. Lift is not really considered, and is not present to any significant extent.
Having said that, for a large high-bypass turbofan, when placed well forward the lifting area can become significant at high angles of attack (whether positive or negative). It can be powerful enough to move the centre of lift forwards, reducing pitch stability and at steep angles leading to a tendency for the angle to diverge further. When Boeing were developing the Max variant of the 737, its new engines suffered just this problem on takeoff and landing. Boeing's solution was to introduce a Manoeuvring Characteristics Augmentation System (MCAS) which automatically operated the elevator to reduce the angle sharply if it got too steep. Tragically, in their hurry they botched the job, two commercial flights crashed fatally and the 737 Max has been grounded indefinitely until they can get a fix certified.

Almost any sort of body, conveniently oriented in a fluid flow, can produce lift. A ball is one of the few exceptions...
Please note that lift and drag do never cancel out, because they are –by definition– vectors at 90º...
There are wingless, heavier-than-air aircraft, like this one, for example:
https://en.wikipedia.org/wiki/Wainfan_Facetmobile

You may get a little "rise" from a ball if it is spinning.

It would produce lift if it where spinning in a convenient way, driven by an external source of torque, so that it might drag the air layers close to its surface, that circulation generating lift. But in the absence of a external torque to produce that spin, I don't think that the ball might spin, and in the absence of spin, there would be no circulation, and hence no lift...

Agree with that.  A golf ball does have spin imparted by the club, producing the Magnus effect.

Most balls have sufficient angular momentum to spin throughout their flight. The phenomenon of spin is extremely familiar to sports players and to cannon and musket gunners. Preventing a ball from spinning is a harder problem than getting it to spin, so there is almost always circulation and lift in one direction or another orthogonal to the flight path. It is known as the Magnus effect.


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How do aircraft follow the tarmac lines while taxiing?
How does the pilot determine he is on the yellow taxi line at all times, since he doesn't have a direct view to the ground below? I am sure there must be some equipment, but I just don't know what.

How do you stay between the lines on the road when driving, when (with many cars) you can't actually see them by looking out the side windows, but only some distance ahead?  Same principle applies to planes.

For most aircraft:
It is just something that you learn. As you approach a line, you have a general sense of where the line is, because you can see the line continue in front of you. This also applies to turning, where you are familiar with the turn radius, and have a sense of where it is. It is similar to a car, in that you can drive down the center line of the road, and still know it is underneath. Scale is just increased.
For tail-draggers:
A tail-dragger is an aircraft that has two front wheels, and one rear wheel, meaning the aircraft is typically pitched up when on the ground. In this situation, the pilot zigzags across the taxiway, looking roughly 30 degrees front left or front right, checking the area in front of him. This isn't so much for following the line though, as it is for ensuring you're not about to hit anything in front of you.

Please let me know if there are any clarifications I can add!

I've added an image of a tail-dragger (or tail-wheel) aircraft just to give you an idea - line of sight is tough!

I'd be very happy zigzagging down the taxiway in that beautiful plane.

As an aside, as you taxi out, if you make the yellow line go right between your legs (you can't look down and see it but you still can tell by other cues as noted in the answer), and make sure you are going in a straight line (i.e. staying right on the yellow line), and memorize the exact spot on the front edge of the cowl (say, like 1 inch right of this particular screw or something) where the yellow line comes into view in front of you, you now have a "gunsight" that will help you deal with left/right visual asymmetry inherent in side-by-side seating.

Put that "gunsight" spot equally high above the horizon (or below as the case may be) in left and right turns at some given airspeed,  The tendency for newer pilots is to tend to put the nose too high in left turns and too low in right turns, if they are sitting in the left seat, because they are "gunsighting" on a spot too close to the centerline of the cowl. Even experienced left-seat pilots may have similar issues when flying from the right seat until they get used to it.

PS likely only practical in tricycle gear a/c because you can't easily look over nose and see yellow line in tailwheel a/c.


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Downwash distribution on basis of Lift distribution
I am new here so I might make some elementary mistakes. Correct me if I am wrong.
I just stumbled upon the downwash distribution for a given lift per unit span distribution along the wingspan. I have attached a photo for your reference.

I was wondering that if we look upon a $dy$, an infinitely small spanwise slice of the wing, then the lift it produces should be proportional to the downwash it created as more downwash equals more distortion which equals more lift. But we can clearly see that at the end where the lift is minimum the downwash is maximum and at the center where the lift is maximum downwash is minimum. Could anyone please explain it?

You are confusing downwash ($w$) with circulation ($\Gamma$). As per Kutta-Joukowski theorem, lift per unit span (in the case of a single lifting line) depends on the distribution of circulation along the wing span:
$$L'(y)=\rho_\infty V_\infty\Gamma(y)$$
If you have an elliptical lift/circulation distribution, the circulation decreases towards zero at the wingtip, therefore lift at the tip is zero. Induced downwash, on the other hand, is constant across the span.

Source: Anderson, Fundamentals of Aerodynamics
You may believe that downwash is the largest at the tip due to the presence of wingtip vortices. However, the vortices are better understood as downwash rollover at the wingtips. The vortices themselves do not contribute to lift generation (but unavoidable for finite span).


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Reason for the multiple sidelobes in an ILS glideslope signal
Why are there multiple side lobes in the glide slope signal from an ILS?

Hi and welcome to the site. I have edited your question to be a bit more adequate. You can also try the physics or amateur radio stack exchange sites, as this question is also firmly in their domains (the reason has to do with antenna radiation patterns)

All directional antennas have sidelobes (and all real antennas are at least somewhat directional). I won't get into detail of the fundamental physics reasons behind that, as that's beyond the scope of the aviation stack exchange, but briefly it's related to diffraction and the Fourier relationship between the aperture distribution and the far-field radiation pattern.
Various design techniques can reduce the amplitude of the sidelobes, sometimes to the point where they're undetectable or at least insignificant. However, these all involve tradeoffs that compromise other performance parameters, size or cost, so if the sidelobes aren't problematic or can be easily avoided operationally, it's not worth trying to suppress them. Also, most glideslope antennas use passive phased-array techniques, and phased arrays are especially prone to sidelobe generation (called grating lobes in that case).

If all antenna have side lobes then why we don’t have it in localiser signal in same strength as they are in glideslope antenna. In localiser, side lobes strength is quite less as compared to glideslope . Why?

@Vikas All antennas have sidelobes but as I stated, some are much worse than others. Localizer antennas and glideslope antennas operate at significantly different frequencies and have very different construction from each other. I'd suggest asking on the Electrical Engineering stack exchange if you'd like to get more into the details of antenna design (and do some background reading beforehand, perhaps Stutzman or Carr)

Thanks buddy for clarification

The ILS transmitting antennas looks to be an array of yagi antennas. Those antennas should have a tight beamwidth, but the penalty for being able to "squirt" energy in a single  direction is that you have multiple sidelobes coming off the side and back side of the antenna. The more antenna elements you add to a single antenna, the more lobes you'll get.
Look at figure 2.1, then compare figure 3.2 and 3.3 at http://www.researchinventy.com/papers/v2i12/E0212026035.pdf
You'll probably get a more in depth answer from the amateur radio guys who are more experienced that I am.


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Was the Horten Ho 229 flying wing a three-point-landing aircraft?
The Ho 229's front wheel is visibly bigger than the main landing gear; during landing, did it touch down on all wheels simultaneously, on the front wheel first, or in the normal manner?

Trying to read deeper into your question, are you asking this because the lack of elevators will make bringing the nose down a bit more difficult? I dont have the answer but I would imagine the Ho-229 would have a pretty flat attitude on landing.

No , but front wheel is  more  bigger than that the two from behind.

The term "3 point landing" is derived from old taildragger (3rd wheel in back) designs.
In reality a 3 pointer is not desirable, as the wheel, front or back, being away from the center of gravity, can produce a nasty pitch if it bounces. At landing speeds this can be uncontrollable.  The term "3 pointer" does imply good landing speed management, as the plane, slightly nose up, has been flared properly, and will "settle" gently to the ground.  Most of the time the pilot will strive to land on the main gear, bleed off more speed, then allow the 3rd wheel down before taxiing off the runway.
The Horton Ho229, if it ever flew, was designed to land under wartime conditions.  Even jets were very vulnerable when slowing to land, and many times paved smooth runways simply were not available (survivable) options.
So the huge front wheel was basically overdesigned for less than perfect landings.  However, landing technique, even for this fantastically futuristic aircraft, would be similar to other planes.


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What is the purpose of these movable panels on the MiG-35?
The MiG-35 has movable panels on the LERX (leading edge root extensions). There are a number of images around the web showing these panels deployed during slow flight and retracted otherwise.
When do they have to use these and what does the use of them change in the flight envelope?

That's more of a leading edge flap.

Here may be a better picture, are you talking about those curved pieces at the root of the wing?

slats not flaps (flaps ar all the way from the root towards the tip of the wings).

Those are Krueger flaps on the Leading Edge Root Extensions ( LERX ).

@George Geo source for your slat/flap definition please?

@Mike Sowsun could you explain why you undid my characterization of these flaps and their location in favor of much more generic terms? If you are thinking these are not high-lift devices, please take note that the grey airframe in your photos, landing with them retracted, is bort 154, an older demonstrator which does not seem to have them. I have edited these particular images out and would like to also revert to the correct terms, unless you want to argue against that :)

They look like glove compartements for the ground crew to me. With the lid come loose.

@PerlDuck that's one hell of a jam on that lid, if it stays open in flight.

@AEhere I have again added 3 photos showing 747, 712, and 702 landing or taking off without these panels extended. I don’t see how they can be called Krueger flaps when we have photographic evidence that they are not used in the “normal” way.

@Mike Sowsun the "normal" way, please specify. Since you do not know whether the planes are taking off or landing, you hardly can judge the appropriate flap setting. In fact, you have, I bet, zero knowledge when it comes to flap settings on MiG-35 or any other russiang fighter jet for that matter, am I right?

Yes, like most people I have zero knowledge of MiG-35 operations, and until someone who does answers this question, I just think it is better to call these "movable panels" instead of  "Krueger Flaps". Krueger flaps are normally used for EVERY takeoff and landing and not left extended AFTER takeoff and landing. These clearly are not being used in like an airliner Krueger flap, so I consider it not to be normal.

@MikeSowsun I am pretty sure your new images are of takeoffs based on the flap configuration. Also note that the image of two MiGs flying in formation was also taken at low speed (based on the vapours and the almost full flaps). I am inclined to call these Krueger flaps because out of Form, Fit and Purpose they seem to have the two first in common with them. The specific usage of flaps varies between airframes and loadouts, but I can see where you-re coming from. Do you also object to the LERX on a similar basis?

They probably are an unconventional use of the traditional Krueger flap, but it would be nice to get confirmation. I don't object to LERX as the MiG-35 clearly has LERX like many other aircraft.

@Mike Sowsun the use of Kruegers  could be seen as "normally" limited to only t/o and ldg, since we are used to seeing them only on airliners. Kruegers are used in high AoA situation, and airliners normally do not operate in such a condition outside the t/o and ldg phase. In general in modern fighters the control surfaces, be they whatever, are cotrolled by computers according to appropriate control laws. Should conditions demand so (high AoA for instance), any surface will be deployed as necessary regardless of the phase of flight.

Usually if the Leading Edge is sharper then this type of flaps would help.

The aerodynamic devices in question here were already present on MiG-29KUB which is a parent version of MiG-35: Wikipedia: MiG-35
The devices are in fact, as some have suggested, Krueger flaps, as Russian test pilot Pavel Vlasov describes in this article: The MiG-29KUB: in the Russian and Indian skies for 9 years

"It is a modern multirole plane with revolutionary fighting capabilities, with an increased payload and a longer list of weapons," said Pavel Vlasov, Honoured Russian Test Pilot, Hero of the Russian Federation, and General Director of the Gromov Flight Research Institute (and Head of the Flying Service at MiG until 2010). He noted at the same time that the MiG-29KUB featured a range of new solutions, such as Krueger flaps, a new flap design, a modern fly-by wire control system, and significantly improved piloting conditions

In addition to calling them Krueger flaps, this article also gives the devices the acronym LEVCON, leading-edge vortex controllers: SlideShare: Fulcrum Reloaded (see page 4)
The purpose of Krueger flaps is to increase the coefficient of lift of the wing, and to improve slow speed handling: Wikipedia: Krueger flap
After facts some speculation: the reason the Krueger flaps are not deployed in some of the pictures with gear extended is probably bacause they are not used in take off configuration, and the pictures most likely have been taken in t/o situation, not while the aircraft is landing

Nice work.  Interesting that the aircraft has slats and flaps on its wing, and the "Kruegers" on its strake. One thing notably learned on this site is the undesirable characteristics of a sharp leading edge at higher AOA.  They may have put a "flap" on there to "soften" the leading edge in situations where more maneuverability is needed. I would look for the computer, or pilot, to close it in situations where less change in AOA is anticipated.

Nice find with that article.

Oh the things one can achieve with google and time to spare :)


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Can Part 141 instrument simulated time be logged?
I'm doing my IR rating in Part 141, and the school says you cannot log simulated time in the logbook, whereas in Part 61 they are allowed. Why?

Do you mean simulator (i.e. approved flight simulator device) time or simulated (i.e. hood) time? If they say you cant log simulated  (hood) time go find another school... If you cant log simulator time, thats up to you. It basically means you have to do all your training in an actual aircraft, might be more pricy but not necessarily a bad thing.

The FAA's Advisory Circular 61-136B addresses this subject and explains how time on an advanced training device should be logged:

D.3 Logging Training Time and Experience.
Authorized instructors
utilizing an FAA-approved ATD for airmen training, pilot time, and
experience requirements are required to log the time as dual
instruction and as basic aviation training device (BATD) or advanced
aviation training device (AATD) time appropriately. Any columns that
reference flight time should remain blank when logging ATD time. ATD
time can only be logged as Instruction Received (Dual), Instrument
Time, or Total Time as reflected on the pilot time section of FAA Form
8710-1, Airman Certificate and/or Rating Application. Simulated
instrument time can be logged in an ATD, but only during the time when
the visual component of the training session is configured for
instrument meteorological conditions (IMC) and the pilot is
maintaining control solely by reference to the flight instruments.
Logging time in this fashion will allow a pilot to credit this time
towards the aeronautical experience and instrument experience
requirements as specified in part 61 or part 141. It is required under
§ 61.51(b)(1)(iv) that the type and identification of the ATD be
included when logging pilot time as described in the letter of
authorization (LOA). It is the responsibility of the flight
instructor, student, or certificated pilot to verify the device is
qualified and approved for training or experience requirements. It
would be appropriate for the person using the ATD to retain a copy of
the LOA. Evaluators such as Designated Pilot Examiners (DPE) are
instructed to request a copy of the LOA from applicants logging ATD
pilot time, to verify the time acquired in the trainer qualifies for
the minimum experience requirements for a certificate or rating.
Note: There are no restrictions on the amount of training accomplished and
logged in training devices. However, the regulatory limitations on
maximum credit allowed for the minimum pilot certification
requirements are specified by parts 61 and 141 and in the LOA. No
approvals or authorizations are provided for aircraft type ratings
using ATDs.

You can log any simulated instrument time with a view limiting device in an aircraft with a legal safety pilot.
You can log simulated instrument time in an aviation training device or simulator when it is:

Approved for training (stated in a letter of authorization [LOA] for
the specific unit.)
It is configured for flight solely by reference to instruments. (set to full IMC conditions/gray screen)
And you log both the model and registration or serial number(found in the LOA) in place of aircraft model and registration. ie Redbird FMX 0071

This logging is parallel to 141 course minimums. In other words you may or may not be able to count a specific flight toward 141 requirements but you can always count it toward your personal totals for part 61 currency, insurance, and job application purposes. For example you may enroll in a 141 instrument course and at some point use a CFI as a safety pilot to practice some simulated instrument under VFR, you can log this toward personal simulated instrument totals but it would not count toward the 35 hour minimum of 141 "instruction" because that requires a CFII.
Now I have heard a persistent incorrect statement from some instructors that claims "Conditions of flight" is only actual flight in a real aircraft, so they do not log simulated instrument time from a ground trainer in that column. Instead they rename some other misc column or use some other kludge. I feel that this practice is not aligned with title 14 CFR part 61.51 (b)(3)iii which explicitly states that logging the condition of flight includes simulated instrument time in full simulators, FTDs, and aviation training devices.
I always recommend including the specific syllabus lesson[s] as a log note if the flight was part of 141 training.

Now the real tricky questions are what is meant by instrument training in part 141 as this is different phrasing than part 61 instrument training. part 61 requires 40 hours flight by reference to the instruments, 141 requires 35 hours of instrument training. To me this implies that its 35 total time, not all on instruments, but that time is approved 141 curriculum.

The second question is if you are a commercial student and use your CFI for a safety pilot for a few minutes during a commercial lesson to stay up on instrument skills how is that logged? It doesn't count as an instrument lesson because they are not a CFII, but is it dual received as part of a commercial lesson and they are a valid safety pilot for logging sim instr time. For example when traveling to and from the maneuver practice area or en route on a cross country flght.


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Why limit the bank angle to 10° when passing through FL300 on a B737-800?
When passing thought FL300, we are instructed to set the bank angle limiter on the MCP to 10°.
I know one of the reasons for this is that we are thrust limited so maneuver capability decreases.
Are there any other reasons?

Welcome to the site. Your question is light on detail, what is this in reference to? Please edit and add more information as at the moment there's no way to answer this.

I assume this is about a Boeing aircraft (bank angle limiter on the MCP). Could you add the tag for the specific aircraft you are asking about? Also, I don't think it has anything to do with thrust-vectoring.

This specification is request on boeing 737 800 .

That's technique only, not Boeing procedure. I fly 737's, and we have no comparable procedure, whatsoever. LNAV doesn't limit bank to 10 degrees above 300, so we don't either. I'll personally take off with 30 degrees selected, then after departure vectors are done, I'll set 20 as the limit. If we get small adjustments ("10 left for traffic") I'd use the lowest limit, but that's just me. For the reason behind this required technique, you'd have to ask your boss. Anything we can offer would be guesswork.

Oh, and, welcome to Av.SE!

One reason that comes to mind is as you get closer to the coffin corner, the extra G force due to maneuvering could cause a stall.  Quoting from "Stall the Pig",

In the thin air at altitude, jets operate within a very narrow
  airspeed band between MMO (redline) and the low-speed limit, typically
  a yellow arc that provides a warning zone prior to a stall, indicated
  by a lower red line. At high altitudes and high weights, this
  band—known as “coffin corner”—can be quite narrow, leaving you a mere
  10 knots of usable airspeed range, for example. Load up the wing in a
  turn and that lower redline will quickly move upward toward your
  airspeed.

By limiting the bank angle, you also limit the G forces, and stay farther away from an accelerated stall.

Amazing they recommend "powering out of a stall" with tweaked out wings and a small Hstab.  Wouldn't power to idle, drop the nose with elevator present a lower risk of correcting AOA without exceeding Vne?  They could get these big airliners up there with a B-52 and do a "drop" test to see if tail flips nose down faster than sink increases AOA in a stall recovery. Still plenty of open desert around Edwards these days.


text:
Why is VNAV and LNAV being prohibited with QFE?
737NG AFM says :

The use of VNAV or LNAV with QFE selected is prohibited.

But what's the reason of this limitation?

For VNAV it seems obvious—it uses baro altimeter and assumes QNH (and STD above transition). But I don't know why it would affect LNAV.

When you set your altimeter to the airport or runway QFE value, the altimeter shows your altitude above the airport or runway threshold:

(source: SKYbrary - Altimeter Pressure Settings)
The altitude limitations on an instrument approach are however specified in altitude above mean sea level (AMSL), which requires setting QNH. When setting QFE you are unable to follow the altitude limitations.
Since you tagged rnp, I guess you are asking about the different ways of flying an RNP approach. This is an example of 3 different minima for an RNP approach:

(minima for the RNP RWY 07L approach at EDDB, Jeppesen)
You can fly this approach in 3 ways:

LNAV: You get lateral guidance from GPS and no vertical guidance. You would start a 3° descent from ODIDO by looking at your ground speed and dialing in the vertical speed from the table:

(vertical profile for the RNP RWY 07L approach at EDDB, Jeppesen)
This is not possible with QFE because you cannot know if you are at 4000 ft AMSL at ODIDO. You also cannot cross check your altitude of 1160 ft AMSL at 3.0 NM to RW07L.

LNAV/VNAV: You get lateral guidance from GPS and vertical guidance is provided by the Baro-VNAV system. This system required the altitude to be in AMSL to provide correct guidance, which is not possible with QFE.
The chart further says:

Baro-VNAV operations not authorized below -15°C.

This is because even with correct QNH set, the altimeter is still not  showing true altitude AMSL due to temperature effects. Colder temperatures mean you are actually lower than indicated, which could potentially be dangerous.

LPV: You get lateral and vertical guidance from GPS using corrections from an SBAS. In this example, the correction signal is coming from EGNOS. Since the vertical guidance is now unrelated to the altimeter, this type of RNP approach can be flown with QFE set.

Awesome. And I saw a saying "FMS database uses barometric as standard and LNAV is linked with turning radius ", not sure whether it's true.

The second case is obvious—all approaches in the database are referenced to altitude AMSL, so that's what you have to use. But for LNAV and flying the altitudes by hand, in countries where flying QFE is common, are there really no approaches encoded in altitudes AFE?

@JanHudec I have never seen it, but it may exist somewhere. This answer says that RAF Northolt is still using QFE, but my Jeppesen approach charts for EGWU all say "Procedure flown with QNH. QFE available by exception.".


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What is the effect of altitude on true airspeed?
I know that wind is taken into account when we compute the TAS(true airspeed) and GS(ground speed). However what is the relationship between the TAS and altitude?
For example: What is the true airspeed on the level flight if the headwind is 20 mph and ground speed is 100 mph at 30,000 feet altitude?

Learn to make the mental calculation of adding 2% to indicated airspeed for every 1000 ft above SL, and you can get a TAS value that is accurate enough for most situations.

If you know GS and local wind speed, the TAS always the same, regardless of altitude. The true airspeed is called "true" because it is exactly how fast you are moving relative to the air. Picture it as a person in a weather balloon (which does not move relative to the surrounding air, i.e., TAS=0), pointing a radar gun at your aircraft to measure its speed. The results would be the same regardless of altitude, temperature, pressure, etc. This is what sets TAS apart from pretty much any other speed like IAS, CAS, EAS and Mach.
Only at truly ridiculous altitudes you would have some problems with calculating TAS, due to the increased orbital radius from the center of the Earth. However, at this point, you're well into the near vacuum of space which means that the whole concept of 'air' speed is quite silly.

Thanks for valuable answer..

Not to mention, in re your last paragraph, that you are dealing as much in plasma dynamics as fluid dynamics at those altitudes.

The true airspeed (TAS) can be calculated from the indicated airspeed (IAS), which is derived from the pitot tubes and static ports, as follows:
$$ \mathrm{TAS} = \mathrm{IAS} \sqrt{\frac{\rho_0}{\rho(a)}} , $$
where $ \rho_0 $ is the air density at sea level and $ \rho(a) $ the air density at altitude $ a $, which depends on pressure $ P $ and temperature $ T $:
$$ \rho(a) = \frac{M \cdot P(a)}{R \cdot T(a)} , $$
where $ M $ is the molar mass of air and $ R $ is the universal gas constant.
Using the international standard atmosphere for $ P(a) $ and $ T(a) $, one can plot the TAS as a function of altitude:

The ground speed (GS) is then given by the vector addition of the TAS and the wind speed:
$$ \mathrm{GS} = \mathrm{TAS} + v_\mathrm{wind} \cos(\alpha) , $$
where $ \alpha $ is the angle between the wind direction and the track of the aircraft ($ \alpha = 0^\circ $ for tailwind, $ \alpha = 180^\circ $ for headwind). This step is independent of pressure or temperature and as such independent of altitude. This means for a given TAS and headwind component, the ground speed is the same at all altitudes (for your example: 100 mph GS with 20 mph headwind implies 120 mph TAS at all altitudes).


text:
What is a registration mark or number?
Does every single aircraft have a unique registration mark or number? If, for example, 2000 Boeing 777 units were produced, do they have their own registration number? And how is that registration number regulated? Who keeps the number? What is that registration intended for?

Related: https://aviation.stackexchange.com/questions/38908/how-are-registration-numbers-assigned

Yes, every aircraft has a registration number--or "tail number" since it is commonly painted on/near the tail. This links each make/model/serial combination to a specific owner, similar to a car's license plate.
Each country assigns tail numbers with that country's unique one-, two- or three-letter prefix(es), e.g. "N" for the USA and "XA" for Mexico, followed by some number of letters and/or digits according to their chosen scheme. Some countries allow requesting a specific number not already in use (or reserved), similar to vanity license plates.
For non-commercial flights, a plane's tail number is used as its radio callsign since it's guaranteed to be unique. Commercial flights typically use the carrier's callsign plus flight number.

Thank you my friend. You made the explanation easy.

So clearly, it is belong to a country, not to an airline company, right?

Yes, in the same way a car license plate number "belongs" to the country that assigns it--even for commercial vehicles.

Thank you my friend.

A historical note: The U.S. used to use NC. The change was made to just N when I was a boy. I think, but am not certain, that antique aircraft that originally were registered with NC are allowed to continue using that.

Not only countries has a prefix (United Nations: 4U), and not all countries have only one prefix (Brazil has PP to PU), see: https://en.wikipedia.org/wiki/List_of_aircraft_registration_prefixes

In the US, Ultralight aircraft (basically weighing under 254 pounds, with some fuel limits and 2 passengers max) are not required to be registered. That does impose some limits on where they area allowed to fly https://www.usua.org/Rules/ruleandregs.htm

@Terry The US has had all of N since 1919. However, N-C, N-L, N-R, and N-X were used for civil aircraft to denote the certificate type until that was abolished a few decades ago (many countries have similar schemes), and now they use just N for all aircraft.

@GiacomoCatenazzi Edited to account for multiple prefixes.  The UN only uses its prefix for its own aircraft, i.e. no other party can register its planes with them, so it's not worth the added complexity.

@StephenS As you say, N was assigned to the U.S. in 1919, and a second letter allowed, which was, as I understand it, C for standard. Thus NC was used until 1948, when new aircraft were required to use just N. More info on https://www.faa.gov/licenses_certificates/aircraft_certification/aircraft_registry/aircraft_nnumber_history/.


text:
What is the average pitch of a plane?
I'm looking for the average pitch of big planes like an Airbus A300. For horizontal travel, is the plane horizontal or does it have a pitch like 1 or 2° (or more)?
If the plane does not accelerate and has a constant speed, is the gravity of the passengers a little backwards?

Does this question help?

@Pondlife I think the OP is looking for hard values in degrees.

Good question. How to get an answer: put your iphone on the floor and use the level app. Turn the phone around and take the average.

I assume by "middle pitch" you're talking about the pitch during cruse? In which case, the answer is, unfortunately, "it depends". Changing pitch changes the amount of lift, and the amount of lift needed depends on the weight of the plane. So, an airplane with more passengers and cargo will need a slightly higher pitch.
Changing speed also changes lift, which will need to be compensated for by changing pitch. However, we're talking about cruise flight here, so speed will remain relatively constant.

You may improve your answer by adding lower and upper bounds (in degrees)

At maximum cruise speed, altitude and payload, most airliners are trimmed into several degrees of pitch-up attitude to maintain constant altitude. At that point, the plane is delicately balanced at those conditions to minimize drag and maximize range.

I think you don't answer the question. The OP is looking for a pitch value and seems aware of cruise pitch attitude.

In the first link of Pondlife, someone said nose-up deck angle is about 2° (0° for fighters and 4° for jets). It’s the kind of aswer I’m looking for. Remember I’m talking about big planes like Airbus with normal charge and not the angle of wings but really the angle of plane with horizontal. Thanks for help :)

IME, at max speed in a Boeing jet (probably not all, but 1 of them), it's about 0-1 deg nose up (as read on the ADI) and at loiter speed at altitude it's about 5 degrees.


text:
How much torque can a Boeing 747 apply when pitching?
I know this is a weird way of thinking about / quantifying this, but I'm trying to figure out how much torque a 747 can apply to itself when it pitches upwards (turning about an axis from wing to wing, with the nose moving upwards). I figure it's equal to the lift times the distance between where lift is applied to the wings and the axis of rotation, but I haven't been able to find this data.

There are a great number of forces torquing a 747 at a time, almost entirely cancelling each other out (hence its stability). Are you asking specifically about the torque induced by the elevator's control surfaces, or also about other forces which would tend to counteract it?

Well, any good answer would need to consider both torque used to overcome rotational inertia and change the pitch rate, and torque used to overcome aerodynamic damping and maintain a steady pitch rate.  Also the "baseline pitch torque" needed simply to maintain linear flight.  Or approach the problem from the other end and look at the max elevator deflection and resulting lift coefficient and figure the aerodynamic force resulting and convert to torque by multiplying by distance to CG.

Raises the question are we looking at NET aerodynamic pitch torque in which case the pitch torque used to overcome aerodynamic damping and maintain a steady pitch rotation rate does not count, and likewise the "baseline" pitch torque used to maintain linear flight does not count-- in this case we can only count the pitch torque component that causes a change in the pitch rotation rate.  So what is the max possible delta pitch rotation rate?  I think you have asked a very hard question perhaps best explored in an accurate simulator.

The question was meant to be "what's the maximum torque it COULD apply to itself, when it's pitching as hard as it can." Total aviation newbie (less than a newbie, not even in the field whatsoever but working on a physics thought experiment).

Though it may be too late to edit the question now without invalidating existing answers, for your thought experiment you might want to be consider whether the flight path is constrained to be linear at the instant that the pitch torque is first applied, or whether the flight path is allowed to be already curving at that instant.  But, I saw in another comment that you were considering the plane to be rolling along on the runway on the landing gear, so maybe that answers that.

Having been a commercial pilot and instructor for over 36 years I deal with this daily. The 747 or any aircraft is essentially balanced at the center of gravity. The positive moment will equal the negative moment on the cg.  The aerodynamic force created by the horizontal stabilizer is easily calculable and is based on the lift coefficient, surface area of the airfoil, velocity, air density (rho),  The forces can range from mere hundreds to thousands of pounds of force applied to the arm depending on these factors.  By the way the cg is generally about 17 to 25% of the mean aerodynamic chord of the 747 measured from the leading edge of the airfoil at the root.
Once the moment (torque) is calculated then pitch acceleration rates based on weight can be determined.  Rates of pitch are only of interest to pilots as they relate to controllability and stability so we don’t worry about actual axial acceleration rates.  In this regard the farther to the rear the calculated cg is within the acceptable range (in relation to the center of lift) the more controllable and aerodynamically unstable the plane will be due to moments being closer to equal.   The farther forward, the more aerodynamically stable and more difficult to control (greater required forces) it will be due to greater nose down moment.
By the way, most planes are designed to fly with some nose down moment due to loading.  This creates a more stable aircraft.  The cg range is always ahead of the neutral point. In theory, were it not for the necessity to longitudinally stabilize the  aircraft very little horizontal stabilizer force would be required. So a small amount of down force is necessary to stay in level flight, by design. This additional downward force adds to the weight of all forces acted upon by the total lift forces.
Tex

It seems you are implying that the neutral point is the point where the tail would generate exactly no upload or download in linear flight.  Is that really true as a general statement?  Could be grounds for another ASE question.  My impression is that many aircraft can be stable even when the CG is located is such that the tail would generate an upward force.  Of course in such a case the CG still must be ahead of the neutral point or else the aircraft would not be stable.

Could be grounds for another ASE question: is the "neutral point" the point where the tail downforce would go to zero in linear flight?  Here's an interesting take on it-- see last two paragraphs-- https://www.av8n.com/how/htm/aoastab.html#sec-pitch-equilibrium

@Thetexan is exactly right.  The NP is the effective balance point about which the tail must react the moment created by the CG forward.  NP is the center of lift but adjusted for other pitching moments that may help or hinder the basic pitching moment of the CG-CL lever.  If I have a seesaw that is in balance on its physical pivot but I add an external influence, like a spring pulling down on one end, that tends to tip it one way, I'd have to move the pivot to a new location to make it balance.  This is the NP.  The NP must ALWAYS be aft of CG to have positive static stability in pitch.

"Trim Drag" is in fact the energy consumed by the tail to generate its downforce.  I can move the CG closer and closer to the NP to reduce the downforce required and thereby reduce trim drag, but I end up with diminishing stability, and to run an airliner with the too far aft like that I have to use electronics and software to drive the tail surfaces in the background to actively make up for it.

The pitching force is coming from the horizontal tail's downforce resisting the airplane's net nose down pitching forces, so the real question is how much downforce is being applied and how far away is the tail's downforce from the lifting forces holding the plane up.
For a given set of parameters, you need to know the All Up Weight, the Center of Gravity location, and the Neutral Point, which is the location of the (gaseous) fulcrum the tail has to work about.  The NP is defined as the longitudinal point at which pitching moments are zero, the "effective" balance point in other words, taking into account the center of lift plus/minus the effects of various pitching moments (airfoil pitching moment, fuselage lift, nacelle lift, thrust effects, flaps and gear hanging down, etc.) which result in the actual net downforce the horizontal tail has to produce to "hold the nose up" in a given steady state flight condition.
If you know the CG location and the all up weight, then the "torque" acting on the fuselage at the Neutral Point is simply all up weight times the distance between the CG and NP.
So if the plane weighed 700,000 lbs, and the CG was 20 feet forward of the NP (just a wild guess; I have no idea the actual number), the "torque" value, the nose-down pitching force acting at the NP, is 14 million foot pounds.  If the aerodynamic center of the tail was 120 ft aft of the NP (another wild guess), that works out to 116666 lbs of downforce required for stable level flight back at the tail.  Of course if you now pull pitch to raise the nose, you are accelerating the mass about the lateral axis now, so those forces go up temporarily.

The values will change with changes in configuration, weight, speed, etc.  Make a change that moves the Neutral Point forward, like adding thrust, and the torque value and downforce required goes down; airplane pitches up from the thrust application because the existing tail downforce is excessive. Drop the gear, which moves the Neutral Point aft, and the torque value and downforce required to counter it goes up; airplane pitches down from the drag of the gear because the existing tail downforce is insufficient.
As far as finding out what is a typical Neutral Point on a 747, good luck with that...

I think this answer could be improved by changing the label (and associated references in text) from "neutral point" to "center of pressure" (or "center of lift").  The center of pressure is the point where we can apply the lift vector without having to also add a pitching moment -- exactly what you've done.  If the CG is at the "center of pressure" then the tail downforce is zero.  The center of pressure moves in flight, thus the preference for using "aerodynamic center" instead, plus a pitching moment.  Regardless, the center of pressure is usually not the same as the Neutral Point.

In other words stable flight is often possible with the CG behind the Center of Pressure (but still ahead of the neutral point), thus causing the tail to generate an upforce rather than a downforce.  Related ASE answer -- https://aviation.stackexchange.com/questions/19388/what-is-the-difference-between-centre-of-pressure-aerodynamic-centre-and-neutra/19399#19399 .  See also https://www.av8n.com/how/htm/aoastab.html#sec-pitch-equilibrium (last two paragraphs).

Center of pressure just refers to the net median point of lifting forces.  Neutral Point also takes into account other pitch moment influences. A low thrust line applies a pitch up moment.  Less tail downforce is required. The NP is moved forward. Dropping the gear creates a nose down pitching moment adding to all the other forces to give a new overall moment.  This moves the NP forward. GG must always be forward of NP so there is a moment that must be opposed by tail downforce. Stabs on jets move LE down to go slower. If the tail was making up force, the stab would have to move the other way.

Regardless of whether tail is making upforce or downforce, lowering the LE of the stab will trim for slower flight.  Well, looks like we're heading for another ASE question here, "Is stable flight possible with tail creating upforce, i.e. with Center of Pressure behind CG".  Or "is it possible for CG to be behind Center of Pressure but still ahead of Neutral Point, yielding stable flight with the tail generating an upforce?"

Well that one has been beaten to death lol.  You could have CG at or aft of the CP but with a strong ND pitching moment induced by some other influence, like floats hanging down, forcing the tail to generate downforce to oppose, you would have some static pitch stability.  I've flown several airplanes with and without floats, and the increased pitch stability with floats installed is subtle but noticeable. The NP must remain aft of the CG in all flight regimes so the operating CG range has to take all that into account.

I assume you are asking about the NET aerodynamic pitch torque that the 747 can generate.  In this case the pitch torque created by tail just to maintain linear flight doesn't count.  Nor does the pitch torque created by the tail to overcome "aerodynamic damping" in the pitch axis during a steady-state (constant airspeed, constant bank angle, constant turn rate) turn.  All that matters is the maximum possible rate of change of the pitch rotation rate, and the aircraft's moment of rotational inertia in the pitch axis.  That is all the information that we need to solve the problem.  Any approach based on other information will lead to a much more complicated solution.
But even boiled down to these simple terms, the problem is very challenging.  It is very difficult to determine the maximum possible rate of pitch rotation.  This is perhaps best determined by experiments in a very accurate simulator, or in the actual aircraft.  Caculating the moment of rotational inertia in the pitch axis is trivial compared to determining the maximum possible rate of change of pitch rotation.
The above notes were aimed at the case where the wheels are off the ground.  When some of the wheels are on the ground, that introduces another complication-- or perhaps a simplification.  When the CG is so far forward that the airplane can only produce a negligible rate of pitch rotation on takeoff at some particular instantaneous airspeed, then the total aerodynamic pitch torque created by the aircraft in that configuration at that airspeed is equal to the pitch torque created by however much weight is still resting on the main wheels at whatever airspeed the aircraft is moving at at that particular instant, times their distance from the CG.  What CG position would cause the aircraft to only be able to cause a negligible rate of pitch rotation at takeoff at some particular airspeed, and how much weight is still resting on the main wheels at that instant, is another thing that might perhaps be explored in a good simulator.
The aerodynamic pitch torque the aircraft can create at a typical rotation airspeed would surely not be the maximum aerodynamic pitch torque the aircraft could create in any situation.
For example, to take a really exotic case-- when the aircraft is inverted at the top of a loop at a relatively low airspeed, gravity is helping to curve the flight path, creating a curvature in the relative wind which essentially has the same effect as bending the fuselage like a banana in the opposite direction (with the concave side toward the wheels/ belly), decreasing effective decalage or creating negative effective decalage.  This would increase the power of the elevator and tail to create an aerodynamic pitch torque, and create a high rate of change in pitch rotation rate, in the landing gear/ belly direction, while decreasing the power of the elevator and tail to create an aerodynamic pitch torque in the opposite direction.  A similar effect was noted in this related answer, which looked at the problem in terms of the elevator's ability (or inability) to keep the wing at a positive-lift angle-of-attack, rather than in terms of the maximum possible rate of change in pitch rotation rotation rate: What has happened to make me experience negative G with the control stick FULL AFT near the top of a loop?

The "torque" created by the nose down pitching moment, CG acting around the neutral point, is present continuously.  In level flight there is a static nose down pitching moment being opposed by tail down force.  If you pull on the stick, you increase the forces but it's a transient condition, same as turbulence.   In a 2 G sustained turn, the level flight static forces are simply doubled.

If it makes things easier, I'm only trying to figure this out at takeoff, and I'm happy to just get within a factor of two. I was under the impression that much of the torque used to lift the nose of the plane at liftoff is generated by the wings, but now I'm realizing it might be more generated by the tail?

At point of rotation it's almost all the leverage applied by the tail to lift the nose, pivoting around the main landing gear, so initially, the lever arm is tail-to-wheel. The "pivot" shifts forward somewhat during the rotation as the wings start generating lift. The peak downforce demand and torque force on the fuselage is about at the point the tail skid contacts the runway.When fuselages get broken on landing, from being "overtorqued" as happened with Beoing's DC-9/717 test a/c, on an Embraer 145  once,  it's on landing, when you add landing G force to the leverage and it's just too much.

@JohnK let's say we chose the CG is the pivot point to resolve our torques around.  This is a valid choice and arguably the one that makes the problem simplest.
Strictly speaking  in level flight the net pitch torque is zero.  Aerodynamic nose-down pitching moment from wing is opposed by aerodynamic  nose-up pitching moment generated by tail; weight itself (or G-load) has no effect on anything.

@JohnK I'm not sure neutral point has any effect on anything no matter what point we choose as the pivot point for our problem, I don't think neutral point is really the same as the point where the airplane would fly with zero tail upload or download if the CG were located there.  Could be grounds for another ASE question.  I think neutral point is the point where the aircraft becomes unstable in pitch if the CG is moved there, and plenty of aircraft are stable even when flying with an upload at the tail.  That too could be grounds for another ASE question.

@JakeKurlander Ok if we are talking about at the point of rotation at takeoff then opposing (nose-down) torque generated by the landing gear comes into the picture so technically my answer should be modified to include that torque as well the change in pitch rotation rate.  When the CG is so far forward that the airplane can only produce a negligible rate of pitch rotation on takeoff then the total aerodynamic pitch torque created by the aircraft is equal to the pitch torque created by how ever much weight is still resting on the main wheels, times their distance from the CG.

The CG must always be forward of the NP to create a nose down moment that tail downforce opposes.  The only time the downforces is not present is in transient maneuvering states.  This is why, to trim to a lower airspeed, the LE of the stab has to move down, increasing its incidence, to maintain the same downforce at the lower speed.  If you slow down without increasing incidence, the plane pitches down.  If you fly with zero tail download, CG balanced on the NP, you are neutrally stable.  The plane won't trim to a speed, will drift any which way in pitch, and be extremely unpleasant to fly.

@JohnK It seems you are implying that the neutral point is the point where the tail would generate exactly no upload or download in linear flight. Is that really true as a general statement? Could be grounds for another ASE question. My impression is that many aircraft can be stable even when the CG is located is such that the tail would generate an upward force. Of course in such a case the CG still must be ahead of the neutral point or else the aircraft would not be stable.

@JohnK Could be grounds for another ASE question: is the "neutral point" the point where the tail downforce would go to zero in linear flight? Here's an interesting take on it-- see last two paragraphs-- av8n.com/how/htm/aoastab.html#sec-pitch-equilibrium

Yes if you look up any definition, the NP is the point at which pitching moments are balanced. If you placed the CG at that spot, there is no pitching moment up or down.  It's the center of lift PLUS/MINUS any external pitching moments that add or subtract to create a "net" center of lift. To have positive static stability in pitch you must have a pitching moment present, a nose-down torque, that is opposed by tail downforce. Speed up, downforce up, pitch up.  Slow down, vice versa.  It's what gives you a trim speed.  CG must always be forward of NP or your airplane is neutral or unstable.

@JohnK see my comments under your answer

Is it possible  to have a stable aircraft (aerodynamically) in a condition where stabilizer updore is necessary for level flight?
No. Not by the definition of static or dynamic stability.
There are two systems that have to be considered.  The first is the wing itself.  The airfoil has a center of pressure that moves fore and aft based on angle of attack.  It also produces a downward force center of pressure due to Bernoulian and Newtonian forces on the bottom of the wing.  The upper and lower centers of pressure are not physically opposite of each other and therefore produces either downward or upward torque on the wing itself.  This torque is centered on the mean aerodynamic center.  The MAC does not move regardless of AOA. It it through this MAC that the center of lift operates.
Now take this wing with Its own system of balances and forces and attach it to a plane with its own balances and forces.  The CL will be behind the CG on most aircraft for stability purposes. Only when the CL and CG are at the same point will the NP be near the CL/CG point.  Since weight and speed determine necessary AOA, and AOA effects CP, drag, and stabilizer AOA the NP (or point where no stabilizer force is required for level flight) will never remain in any one location but will be at a different point based on a given set of conditions.  The odds of the CG and NP ever being and staying the same are improbable.
As to how much torque is required....torque is torque.  You can simple calculate the moments of a plane that is balanced.   The force required to move a 400,000 lb airplane about its CG will be a matter of F=ma.  That will give rate for a given force.  Calculate the force capable with a 747 stabilizer (per L=ClrhoV^2*S) and apply it to the force formula and that should be close to the rate or rotational movement around the lateral axis.  My angular momentum physics may be a little rusty.
Angle of incidence also plays into this.  Most airplanes have a positive AOI.  A B727 had an almost 1.5 degree down AOI.
That’s why it always flew nose up compared to other planes
tex

Welcome to ASE.  It looks like at least part of this answer would be better posted to a different question; there are several existing questions on ASE that this answer might fit.  Also on ASE, people are welcome to ask a question and then self-answer it, so that's another option if you feel this answer best fits a question that has not been asked yet.  But consider this one -- https://aviation.stackexchange.com/questions/22087/do-any-airplane-designs-exist-that-dont-involve-a-flight-surface-that-provides

"A B727 had an almost 1.5 degree down AOI."-- really?  I wonder why.  I see another ASE question coming here...